PLC英文文献翻译.docx

PLC英文文献翻译.docx

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PLC英文文献翻译

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PLCtechniquediscussionandfuturedevelopment

Alongwiththedevelopmentoftheages,thetechniquethatisnowadaysisalsograduallyperfect,thecompetitionplaysmorestrong;theoperationthatlistdependstheartificialhasalreadycan'tsatisfiedwiththecurrentmanufacturingindustryforeground,alsocan'tguaranteetherequestofthehigherquantityandhighnewtheimageofthetechniquebusinessenterprise.

Thepeopleseeinproducepractice,automatebroughtthetremendousconvenienceandtheproductquantitiesforpeopleupofassurance,alsoeasedthepersonnel'slaborstrength,reducetheestablishmentonthepersonnel.Thetargetcontrolofthehardrealizationinmanycomplicatedproductionlines,wholeandexcellentturn,thebestdecisionetc.,well-trainedoperationwork,technicalpersonnelorexpert,governorbutcanjudgeandoperateeasily,canacquirethesatisfiedresult.Theresearchtargetoftheartificialintelligencemakesuseofthecalculatorexactlytocarryout,imitatetheseintelligencesbehavior,moderatingtheworkthroughperson'sbrainandcalculators,withthemodethatperson'smachinecombine,forresolvetheverycomplicatedproblemtolookforthebestpath

Wecomeinsightofthecontrolthatlinksaftertheelectricappliancesinvarioussituation,thatisalreadythethattimegenerationpast,nowofafteruseinthemoldaperhapssimpleequipmentsofgrass-rootscontrolthattheelectricappliancescandoforthelowlevelonly;AndthePLCemergencealsobecametheepoch-makingtopic,addingthevividsoftwarecontrolthroughaveryandstablehardware,makingtheautomationheadforthenewhightide.

ThePLCbiggestcharacteristicsliein:

Theelectricalengineeringteacheralreadynolongerelectrichardwareuptoomanycalculationsofcost,aslongasordertheimportationthatthebuttonswitchortheimportationofthesensorsordertolinkthePLCupcansolveproblem,passtooutputtoordertheconjunctioncontactmachineorcontrolthestartequipmentsofthebigpoweraftertheelectricappliances,buttheexportationequipmentsdirectconjunctionofthesmallpowercan.

PLCinternalcontainmenthavetheCPUoftheCPU,andtaketohaveanI/Oforexpandofexteriortoconnectapeople'saddressandsavingmachinethreebigpiecestoconstitute,CPUcoreisfromanormanyistiredtoaddthemachinetoconstitute,mathematicsthattheyhavethelogicoperationability,andcanreadtheproceduresavethecontentsofthemachinetodrivethehomologoussavingmachineandI/Ostoconnectafterpassthecalculation;TheI/Oaddinnerpartistiredtheinputandoutputsystemofthemachineandexteriorlink,anddeposittherelateddataintotheproceduresavingmachineordatasavingmachine;ThesavingmachinecandepositthedatathattheI/Oinputinthesavingmachine,andinworkadjustingtobecometiredtoaddthemachineandI/Ostoconnect,savingmachineseparatelysavingmachineRAMoftheproceduresavingmachineROManddates,theROMcandodepositofthedatapermanenceinthesavingmachine,butRAMonlyfortheCPUcomputesthetemporarycalculationusageofhourofbufferspace.

ThePLCanti-interferenceisveryandexcellent,ourrootneednotconcernitsservicelifeandtheworksituationbad,theseallproblemshavealreadynolongerbecomethetopicthatwefail,butstaytoourisaconcerntocometointernalresourcesofmakeuseofthePLCtostrengthenthecontrolabilityoftheequipmentsforus,makeourequipmentsmoregentle.

PLClanguageisnotweimagineofeditcollectedmaterialsthelanguageorlanguageofCstocarryonweavingthedistance,butthetrapezoiddiagramthattheadoptionisoriginalaftertheelectricappliancestocontrol,maketheelectricalengineeringteacherwhileweavingtowritetheprocedureveryeasycomprehendedthePLClanguage,andalotofnon-electricityprofessionalalsoveryquicklyknowandgodeepintotothePLC.

TounderstandthePLC'scommunicationsversatility,let'sfirstdefinethetermsusedindescribingthevarioussystems.

ASCII:

Thisstandsfor"AmericanStandardCodeforInformationInterchange."AsshowninFig.1,whentheletter"A"istransmitted,forinstance,it'sautomaticallycodedas"65"bythesendingequipment.Thereceivingequipmenttranslatesthe"65"backtotheletter"A."Thus,differentdevicescancommunicatewitheachotheraslongasbothuseASCIIcode.

ASCIImodule:

ThisintelligentPLCmoduleisusedforconnectingPLCstootherdevicesalsocapableofcommunicatingusingASCIIcodeasavehicle.

Bustopology:

Thisisalinearlocalareanetwork（LAN）arrangement,asshowninFig.2A,inwhichindividualnodesaretappedintoamaincommunicationscableatasinglepointandbroadcastmessages.Thesemessagestravelinbothdirectionsonthebusfromthepointofconnectionuntiltheyaredissipatedbyterminatorsateachendofthebus.

CPU:

Thisstandsfor"centralprocessingunit,"whichactuallyisthatpartofacomputer,PLC,orotherintelligentdevicewherearithmeticandlogicaloperationsareperformedandinstructionsaredecodedandexecuted.

Daisychain:

ThisisadescriptionoftheconnectionofindividualdevicesinaPLCnetwork,where,asshowninFig.3,eachdeviceisconnectedtothenextandcommunicationssignalspassfromoneunittothenextinasequentialfashion.

Distributedcontrol:

Thisisanautomationconceptinwhichportionsofanautomatedsystemarecontrolledbyseparatecontrollers,whicharelocatedincloseproximitytotheirareaofdirectcontrol（controlisdecentralizedandspreadoutoverthesystem）.

Hostcomputer:

Thisisacomputerthat'susedtotransferdatato,orreceivedatafrom,aPLCinaPLC/computernetwork.

Intelligentdevice:

ThistermdescribesanydeviceequippedwithitsownCPU.

I/O:

Thisstandsfor"inputsandoutputs,"whicharemodulesthathandledatatothePLC（inputs）orsignalsfromthePLC（outputs）toanexternaldevice.

Kbps:

Thisstandsfor"thousandbitspersecond,"whichisarateofmeasureforelectronicdatatransfer.

Mbps:

Thisstandsfor"millionbitspersecond."

Node:

Thistermisappliedtoanyoneofthepositionsorstationsinanetwork.Eachnodeincorporatesadevicethatcancommunicatewithallotherdevicesonthenetwork.

Protocol:

Thedefinitionofhowdataisarrangedandcodedfortransmissiononanetwork.

Ringtopology.ThisisaLANarrangement,asshowninFig.2C,inwhicheachnodeisconnectedtotwoothernodes,resultinginacontinuous,closed,circularpathorloopformessagestocirculate,usuallyinonedirection.Someringtopologieshaveaspecial"loopback"featurethatallowsthemtocontinuefunctioningevenifthemaincableissevered.

RS232.ThisisanIEEEstandardforserialcommunicationsthatdescribesspecificwiringconnections,voltagelevels,andotheroperatingparametersforelectronicdatacommunications.TherealsoareseveralotherRSstandardsdefined.

Serial:

Thisisanelectronicdatatransferschemeinwhichinformationistransmittedonebitatatime.

Serialport:

Thisthecommunicationsaccesspointonadevicethatissetupforserialcommunications.

Startopology.ThisisaLANarrangementinwhich,asshowninFig.2B,nodesareconnectedtooneanotherthroughacentralhub,whichcanbeactiveorpassive.Anactivehubperformsnetworkdutiessuchasmessageroutingandmaintenance.Apassivecentralhubsimplypassesthemessagealongtoallthenodesconnectedtoit.

Topology:

ThisrelatestoaspecificarrangementofnodesinaLANinrelationtooneanother.

Transparent:

Thistermdescribesautomaticeventsorprocessesbuiltintoasystemthatrequirenospecialprogrammingorpromptingfromanoperator.

Nowthatwe'refamiliarwiththeseterms,let'sseehowtheyareusedindescribingtheavailablePLCnetworkoptions.

PLCnetworkoptions

PLCnetworksprovideyouwithavarietyofnetworkingoptionstomeetspecificcontrolandcommunicationsrequirements.TypicaloptionsincluderemoteI/O,peer-to-peer,andhostcomputercommunications,aswellasLANs.Thesenetworkscanprovidereliableandcost-effectivecommunicationsbetweenasfewastwoorasmanyasseveralhundredPLCs,computers,andotherintelligentdevices.

ManyPLCvendorsofferproprietarynetworkingsystemsthatareuniqueandwillnotcommunicatewithanothermakeofPLC.Thisisbecauseofthedifferentcommunicationsprotocols,commandsequences,error-checkingschemes,andcommunicationsmediausedbyeachmanufacturer.

However,itispossibletomakedifferentPLCs"talk"tooneanother;what'srequiredisanASCIIinterfacefortheconnection（s）,alongwithconsiderableworkwithsoftware.

RemoteI/0systems

AremoteI/Oconfiguration,asshowninFig.4A,hastheactualinputsandoutputsatsomedistancefromthecontrollerandCPU.Thistypeofsystem,whichcanbedescribedasa"master-and-slave"configuration,allowsmanydistantdigitalandanalogpointstobecontrolledbyasinglePLC.Typically,remoteI/OsareconnectedtotheCPUviatwistedpairorfiberopticcables.

RemoteI/Oconfigurationscanbeextremelycost-effectivecontrolsolutionswhereonlyafewI/Opointsareneededinwidelyseparatedareas.Inthissituation,it'snotalwaysnecessary,orpracticalforthatmatter,tohaveacontrollerateachsite.NorisitpracticaltoindividuallyhardwireeachI/OpointoverlongdistancesbacktotheCPU.Forexample,remoteI/Osystemscanbeusedinacquiringdatafromremoteplantorfacilitylocations.Informationsuchascycletimes,counts,durationorevents,etc.thencanbesentbacktothePLCformaintenanceandmanagementreporting.

InaremoteI/Oconfiguration,themastercontrollerpollstheslavedI/Oforitscurrent